/*

 Copyright 2012 Peter Dornbach.

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
   
*/

package com.dornbachs.zebra.guitarear;

import java.util.Collection;
import java.util.TreeMap;

public class ReservoirSampler<T> {
	public ReservoirSampler(int maxNumSamples) {
		_samples = new TreeMap<Double, T>();
		_maxNumSamples = maxNumSamples;
	}
	
	public void add(T sample, double weight) {
		// Based on http://gregable.com/2007/10/reservoir-sampling.html
		final double key = Math.pow(Math.random(), 1.0 / weight);
		_samples.put(key, sample);
		if (_samples.size() > _maxNumSamples) {
			_samples.remove(_samples.firstKey());
		}
	}
	
	public Collection<T> getSamples() {
		return _samples.values();
	}

	private int _maxNumSamples;
	private TreeMap<Double, T> _samples;
}
